Unprecented floods on the Mississippi, in Colombia, and Canada

The great Mississippi River flood of 2011 continues to make history, with Saturday's opening of the flood gates of the Morganza Spillway marking just the second time that flood control structure has been used since its construction in 1956. With the Morganza, Bonnet Carre', and Birds Point-New Madrid Spillways all open, the Army Corps of Engineers has now opened all of its major spillways simultaneously for the first time ever. The Mississippi is rising at Vicksburg, Mississippi, where the water has now reached 56.5', exceeding the previous all-time record of 56.2', set during the great flood of 1927. Natchez, Mississippi, is also at its greatest flood height on record, with the water at 60.6'. The previous record high was 58', set in 1937. However, the opening of the Morganza spillway has reduced the predicted heights of the great flood of 2011 from Natchez to New Orleans by 1 to 1.5'. This will serve to greatly reduce the pressure on the levees and on the Old River Control Structure, which as I discussed in my previous post, is America's Achilles' heel, and must be protected. According the National Weather Service, flood heights along the Lower Mississippi from Natchez to New Orleans will peak this week, and slowly fall next week. Rainfall over the next five days is expected to be minimal over the Lower Mississippi watershed. The next chance for significant rain over the region will come Sunday, May 22.

Figure 1. Saturday's opening of the first gate on the Morganza Spillway, as seen on the live feed from USTREAM.

Devastating flooding continues in ColombiaDevastating flooding has hit South America in Colombia, where exceptionally heavy spring rains have killed at least 425 people so far this year, with 482 others missing. Damages are in the billions, and there are 3 million disaster victims. "Some parts of the country have been set back 15 to 20 years", said Plan’s Country Director in Colombia, Gabriela Bucher. "Over the past 10 months we have registered five or six times more rainfall than usual," said the director of Colombia's weather service, Ricardo Lozano. Up to 800 mm (about 32 inches) of rain has fallen along the Pacific coast of Colombia over the past two weeks (Figure 3). The severe spring flooding follows on the heels of the heaviest fall rains in Colombia's History. Weather records go back 42 year in Colombia. Colombia's president Juan Manuel Santos said, "the tragedy the country is going through has no precedents in our history." The 2010 floods killed 571 people--the second deadliest year for floods in Colombian history, next to 1987. The floods did over $1 billion in damage, and affected 2.8 million people. In many places, the flood waters from this great disaster never fully receded, and are now rising again due to this latest round of intense flooding. More rain is in the forecast--the latest forecast from the GFS model calls for an additional 5 - 10 inches (200 - 400 mm) across much of western and northern Colombia in the coming week.

Figure 2. Satellite-observed rainfall over Colombia during the past two weeks shows a region of up to 800 mm (about 32 inches) has fallen near the Pacific coast. Image credit: Navy Research Lab, Monterey.

Colombia's rainy season usually has two peaks: one the fall in October, then then another in the spring in April - May. The heavy rains are due to the presence of the Intertropical Convergence Zone, the area encircling the earth near the Equator where winds originating in the northern and southern hemispheres come together. When these great wind belts come together (or "converge", thus the name "Convergence Zone"), the converging air is forced upwards, since it has nowhere else to go. The rising air fuels strong thunderstorm updrafts, creating a band of very heavy storms capable of causing heavy flooding rains. In La Niña years, when a large region of colder than average water is off the Pacific coast of Colombia, rainfall tends to increase over Colombia. La Niña was moderate to strong during the fall 2010 rains and floods in Colombia, and was largely to blame for Colombia's deadly rainy season. However, in recent months, La Niña has waned. April sea surface temperatures off the Pacific coast of Colombia (0° - 10°N, 85° - 75°W), warmed to the 13th highest temperatures in the past 100 years, 0.68°C above average. Thus, this month's flooding in Colombia may not be due to La Niña.

Figure 3. Dramatic video of flooding in Colombia over the weekend. Flood waters swept away cars and buses in a busy street in the city of Barranquilla, and passengers climbed on the roofs of their vehicles in order to escape the flood waters. Video credit: BBC.

300-year flood in Canada; wildfires destroy large portions of Slave Lake, AlbertaIn Manitoba, Canada, heavy spring snow melt in combination with heavy rains have combined to create record flooding on the Assiniboine River. Authorities intentionally breached a levee over the weekend to save hundreds of homes, but inundated huge areas of farmland as a result. The flood is being called a 300-year flood, and damages are already in excess of $1 billion. In Alberta, Canada, reverse extreme is causing havoc: severe drought and strong spring winds have made ideal conditions for wildfires, which swept into the community of Slave Lake (population 6,700) yesterday. The fires destroyed hundreds of buildings, burning down the town hall and at least 30% of the town, according to preliminary media reports.

Figure 4. Video of the May 15, 2011 Slave Lake fire.

First tropical wave of the year over the AtlanticThe first tropical wave of 2011 is now over the tropical Atlantic near 6°N 46°W, according to the latest Atlantic Tropical Weather Discussion. The wave will bring heavy rain to the northeast coast of South America over the next two days, but is too far south to be a threat to develop into a tropical depression. The Atlantic hurricane season is just two weeks away, and the Eastern Pacific hurricane season began yesterday. So far, the models are not predicting any tropical storm development in the East Pacific or Atlantic over the next six days.

Flash floods, not overall flooding. Last week we had some torrential rainfalls in the PR/VI area that dropped 4+ inches in under an hour and the ground is fairly well saturated in some areas as a result. Currently (1730 hrs Atlantic Time) we are getting some heavy rain on St. Croix but it is in short bursts. Guts and low-lying areas my experience some temporary flooding or even flash floods in steeper areas. PR will be experiencing the same, but they have more steep mountains and real rivers to deal with the runoff. Should be fine for the most part.

Flash flooding. We're having some heavy rains as I type this and PR is getting the same or maybe a bit worse. Ground is fairly saturated from last week's torrential rains so things could get hairy but the storm picture doesn't look that bad just yet.

Coffee deprivation here too didn't even notice. The link is "good" just apparently the model there hasn't been run for awhile.. Your link isn't fairing any better for us either. got another? I'll have another cup of coffee.

Here, here! We had a tiny taste of it with the last front.Feast or famine so far this year.Floods, droughts, tornados and wildfires.My friend in Stuttgart reports unseasonally warm temperatures there for April and May.I wonder what this all means.Have a great day everyone.Live, Love, Laugh, Smile.Sometimes less is more. :)

One of the hottest and driest Aprils on record in France has parched farmland and cut water reserves, stoking worries of a drought similar to that experienced in 1976 and fuelling concern harvests will suffer in the European Union's top grain producer.

No substantial rainfall is expected in the next two weeks, weather expert Michele Blanchard told Monday's press conference.

In an interview with Reuters Insider, Meteo France forecaster Michel Daloz said that temperatures would also rise sharply in the next week, boosting groundwater evaporation.

So south Texas will stay dry. I tried playing the All Stars rain dance out in my back yard on my laptop, but the grass is still crunching when I walk on it. Sigh.I would LOVE to see just a teeny-tiny tropical storm come along.

RastaSteve - as for WU being "inaccurate", its not so much a matter of inaccuracy, but more of an issue known as GIGO. Garbage In, Garbage Out. If the PWS stink, the data will stink. WU has the same data feed from airports as the NWS, so they have the same info.

Also, just an observation I know has been made by many, but you've been predicting and talking about "the rainy season" for a good month and a half now. The rains will come when the rains come.

Good Morning.The very low levels of Sahara Dust right now is pretty unusual for this time of year.If we accept that dust is part of the recipe for T-Waves off Africa not being able to develop into potential T-Storms, then this is another bad sign for this coming season.

Note that Sahara Dust is NOT proven to be either a detriment or a encouragement to Storm development. Research continues...But it does seem to me that Dust indicates dry air, and storms would be more likely to have a chance at development in dust-free environments.This has been the observed norm in the past 5 years or so.